The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of IC processing and manufacturing. For these advances to be realized, similar developments in IC processing and manufacturing are needed. For example, the need to perform higher resolution lithography processes grows.
One lithography technique is extreme ultraviolet lithography (EUVL). The EUVL employs a photomask to be exposed in the extreme ultraviolet (EUV) region so as to form a pattern on a substrate. Generally, a photomask employed in the EUVL is referred to as a EUV photomask. Light in the EUV region has a wavelength in the range from about 1 nm to about 100 nm.
While existing lithography techniques have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect. For example, the reuse of EUV photomasks in EUVL processes has given rise to issues.